Bass w/out the box

Kornbread

   I seem to be very good at starting new projects before finishing the old ones ... so why stop now.

   There are 4 15" Dayton IB385-8 sitting in their IB cube out in the shed.  Neighbor's trailer sits way too close to the shed and he doesn't plan on moving anytime soon, so more more than likely they'll never get used again.  Time to re-purpose em'. 

     Craig got the mental juices flowing with his ob project.  Instead of a standard ob configuration, what about this (is it more commonly called a w frame woofer?) it can be found here, and IIRC, the Hurricane build in PE's gallery may operate under the same principle;  http://http//www.linkwitzlab.com/woofer3.htm 

   Where can modeling software be found for this type of configuration as well as the midrange (mathcad?) and tweet placement on, and size of, an ob arrangement?  What works, what doesn't?    

jhollander

I use ABC dipole to get an idea where to cross and the loading.  There are several other programs that will give you the baffle response.  H, W, and U frames all have a cavity resonance, so typically you want to cross below 200 Hz or so.  This makes the use of an electronic x-o pretty appealing, although many still go passive (Eric, Adam, etc.).

Flat baffle lets you cross up as high as the first dipole null which for woofer is close to 1K depending on the width.

I can run a few sims if you want.  Of course the easiest solution would be to come by and pick up some purple speakers, then you can experience OB bass and highs for the price of gas.

Kornbread

John, I'd love to visit some time.  Due to a fire in another plant, work has been extremely slow the past ~6 weeks and is just now returning to normal.  My paycheck has been tiny.  With that said, there are a few ebay audiophiler caps on the way, with magnet wire, resisters, and more caps to come later.  It would be great to finally finish up a project and haul it up there for some constructive criticism. 

Have more of the axp06 and carbon fibre cp's from the mcm buyout that might work for mids. 

I'll have to check out abc.     

Kornbread

Had to move lots of stuff but the Dayton IB's are now liberated from their corner.  No scratchy sounds when moving the cones or mice holes. 

  

Kornbread

Playing around.  Had some scraps about 30" long so decided to slap together a 30" u-frame.  It will need shortened but time to experiment. 

        

ABC worked but now it doesn't.  Allowed macros and both analysis toolpak and vba are active.  Yes, I'm no good with computers.    

What works best for measuring this type of woofer?  Does it need to be away from boundaries like when measuring other speakers?  It's heavy but I should be able to get it onto some saw horses.  

The ABC preview showed the first rez at 144hz and the second at 300hz.  This is the measurement with the mic at 1 meter and about 8" off the floor.  The first and second rez are on the mark although the rest of the response doesn't look to great.  Purple trace is with no damping, Green is with a bit more than two pillows worth of poly.       

     

   

dats damped/not damped. 

   

jhollander

Away from boundaries would be the best to see the baffle step and roll off.  I've also close mic'ed, you should be able to see the cavity resonances. 

On the music and design website there are instructions for measuring both the driver and the back u-frame exit and combining.

If you were matching/ stacking a TM then I'd measure from the TM axis location to get the spl match right.